For certain types of calls, it can be advantageous to obtain information regarding the location of the caller. For example, when a Public Safety Answering Point (PSAP) answers an emergency-services call, it is desirable for the PSAP to be able to automatically determine the location of the caller in order to quickly dispatch assistance to that location. For calls made from landline phones, which typically have fixed locations, the PSAP usually determines the caller's location based on the calling-party number included in the SS7 or other signaling that is used to route the call to the PSAP. In particular, the PSAP may consult a database, such as an Automatic Location Identification (ALI) database, to determine what physical location is associated with the landline calling-party number.
For calls made using a wireless phone and a wireless wide area network (WWAN), however, difficulty can arise because the wireless phone is mobile and is thus not associated with a fixed location. Furthermore, for calls made using a voice-over-IP capable phone (whether wired or wireless), additional difficulty can arise because such a phone may be connected to virtually any network port (at any location) when the phone initiates the call.